The present invention relates to an inorganic particle-containing composition, a transfer film comprising the same and a plasma display panel production process.
In recent years, much attention has been paid to a plasma display as a plate-like fluorescent display. FIG. 1 is a diagram typically showing the section of an AC plasma display panel (to be abbreviated as xe2x80x9cPDPxe2x80x9d hereinafter). In FIG. 1, reference numerals 1 and 2 denote glass substrates which are opposed to each other, and 3 a barrier. Cells are formed by the glass substrate 1, the glass substrate 2 and the barrier 3. Denoted by 4 is a transparent electrode fixed on the glass substrate 1, 5 a bus electrode formed on the transparent electrode 4 to reduce the resistance of the transparent electrode 4, 6 an address electrode fixed on the glass substrate 2, 7 a fluorescent material held in each cell, 8 a dielectric layer formed on the surface of the glass substrate 1 to cover the transparent electrode 4 and the bus electrode 5, 9 a dielectric layer formed on the surface of the glass substrate 2 to cover the address electrode 6, and P a protective film made from magnesium oxide, for example.
A color filter (red, green or blue) or a black matrix may be formed between the glass substrate and the dielectric layer to obtain a high-contract image in a color PDP.
There is known a method of forming the dielectric layer 8 which comprises preparing a pasty inorganic particle-containing composition (glass paste composition) containing glass powders, a binder resin and a solvent, coating the glass paste composition on the surface of the glass substrate 1 by a screen printing method, drying it to form a film forming material layer, and baking this film forming material layer to remove the organic substances and sinter the glass powders.
As the binder resin forming the glass paste composition, there are known cellulose derivatives such as methyl cellulose, ethyl cellulose and carboxymethyl cellulose, polyvinyl alcohol""s, polyvinyl butyral, urethane-based resins and melamine-based resins. Out of these, ethyl cellulose is preferred from the viewpoints of the dispersibility of glass powders, the coating properties of the composition and flammability (refer to JP-A 6-321619) (the term xe2x80x9cJP-Axe2x80x9d as usedherein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d).
The thickness of the film forming material layer formed on the glass substrate 1 must be 1.3 to 2.0 times the thickness of the dielectric layer 8 to be formed in consideration of a reduction in the thickness of the film caused by the removal of the organic substances in the baking step. For example, to adjust the thickness of the dielectric layer 8 to 20 to 50 xcexcm, a film forming material layer having a thickness of 30 to 100 xcexcm must be formed.
When the glass paste composition is coated by a screen printing method, the thickness of the coating film formed by a single time of coating is about 15 to 25 xcexcm. Therefore, to form the film forming material layer having a predetermined thickness, the glass paste composition must be coated on the surface of the glass substrate a plurality of times, for example, 2 to 7 times (multiple printing).
However, when the film forming material layer is formed by multiple printing making use of the screen printing method, the dielectric layer formed by baking the film forming material layer does not have uniform thickness (for example, a tolerance of xc2x15 % or less). This is because it is difficult to coat the glass paste composition uniformly on the surface of the glass substrate by multiple printing making use of the screen printing method. As the coating area (panel size) and the number of times of coating increase, nonuniformity in the thickness of the dielectric layer becomes larger. A panel material (glass substrate having the dielectric layer) obtained by the step of coating by multiple printing has nonuniform dielectric characteristics caused by thickness nonuniformity within the plane and nonuniform dielectric characteristics cause surface defects (brightness nonuniformity) in a PDP.
Further, the mesh form of a screen plate may be transferred to the surface of the film forming material layer in the screen printing method and a dielectric layer formed by baking this film forming material layer is inferior in surface flatness.
As means of solving the above problems when the film forming material layer is formed by the screen printing method, the inventors of the present invention have proposed a PDP production process comprising the steps of coating a glass paste composition on the surface of a base film, drying the coating film to form a film forming material layer, transferring the film forming material layer formed on the base film to the surface of a glass substrate having electrodes fixed thereon and baking the transferred film forming material layer to form a dielectric layer on the surface of the glass substrate (may be referred to as xe2x80x9cdry film methodxe2x80x9d hereinafter)(refer to JP-A 9-102273).
According to this production process, a dielectric layer having excellent thickness uniformity and surface uniformity can be formed.
The present inventors have also proposed a composite film comprising a base film, a film forming material layer obtained from a glass paste composition and a cover film which is formed on the surface of the film forming material layer and can be peeled off easily as a transfer film which can be suitably used for the formation of the dielectric layer of a PDP (refer to JP-A 9-101653).
This composite film (transfer film) is advantageous because it can be kept in the form of a roll.
The present inventors have further proposed a method of forming a barrier, electrode, resistor, dielectric layer, phosphor, color filter and black matrix which are the constituent elements of a PDP, which comprises the steps of coating a pasty inorganic particle-containing composition on the surface of a base film to form a film forming material layer (transfer film), transferring the film forming material layer formed on the base film to the surface of a substrate, forming a resist film on the transferred film forming material layer, exposing the resist film to form a resist pattern latent image, developing the resist film to form a resist pattern, etching the film forming material layer to form a pattern layer corresponding to the resist pattern and baking the pattern layer (refer to JP-A 9-340514).
However, when the film forming material layer is formed by coating a glass paste composition (inorganic particle-containing composition) containing a conventionally known resin such as a cellulose derivative on the surface of a base film (a transfer film is produced), the formed film forming material layer is not so flexible that the surface of the film forming material layer is finely cracked if the transfer film is bent.
A transfer film comprising a film forming material layer with unsatisfactory flexibility is inferior in suppleness and is difficult to be rolled.
Since the film forming material layer containing a cellulose derivative cannot exhibit sufficient adhesion (thermal adhesion) to the glass substrate, it is difficult to transfer the layer from the base film to the surface of the glass substrate.
To cope with these problems, the present inventors have found that a transfer film having excellent transferability of the film forming material layer (adhesion to the glass substrate) can be obtained by preparing a glass paste composition containing an acrylic resin as a binder resin and coating the glass paste composition on the surface of a base film.
However, the film forming material layer formed by coating the glass paste composition containing an acrylic resin on the surface of the base film still does not have sufficient flexibility.
As means of providing flexibility to the film forming material layer constituting a transfer film, there is conceivable a method of forming a film forming material layer by preparing a glass paste composition containing an acrylic resin having high flexibility and coating the glass paste composition on the surface of a base film.
However, the acrylic resin having high flexibility may not be completely decomposed and removed in the step of baking the film forming material layer and part of the acrylic resin may remain in the formed sintered body (for example, a dielectric layer composed of a glass sintered body) and color the dielectric layer, thereby impairing its light transmission properties.
The present invention has been made under the above circumstances.
It is a first object of the present invention to provide an inorganic particle-containing composition capable of forming a constituent element (for example, a barrier, electrode, resistor, dielectric layer, phosphor, color filter or black matrix) of a PDP advantageously.
It is a second object of the present invention to provide an inorganic particle-containing composition capable of forming a glass sintered body (for example, a dielectric layer constituting a PDP) having high light transmittance.
It is a third object of the present invention to provide an inorganic particle-containing composition capable of producing a transfer film comprising a film forming material layer having excellent flexibility.
It is a fourth object of the present invention to provide an inorganic particle-containing composition capable of producing a transfer film having excellent transferability, that is, heat adhesion of a film forming material layer to a substrate.
It is a fifth object of the present invention to provide a transfer film capable of forming a constituent element of a PDP efficiently.
It is a sixth object of the present invention to provide a transfer film comprising a film forming material layer having excellent flexibility.
It is a seventh object of the present invention to provide a transfer film having excellent transferability (heat adhesion to a substrate) of a film forming material layer.
It is an eighth object of the present invention to provide a PDP production process capable of forming a constituent element of a PDP efficiently.
It is a ninth object of the present invention to provide a PDP production process capable of forming a PDP having the high position accuracy of a constituent element.
It is a tenth object of the present invention to provide a PDP production process capable of forming a dielectric layer having large thickness efficiently.
It is an eleventh object of the present invention to provide a PDP production process capable of forming a dielectric layer required for a large panel efficiently.
It is a twelfth object of the present invention to provide a process for producing a PDP having a dielectric layer with excellent thickness uniformity.
It is a thirteenth object of the present invention to provide a process for producing a PDP having a dielectric layer with excellent surface flatness.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by an inorganic particle-containing composition comprising:
(A) inorganic particles;
(B) a binder resin; and
(C) at least one plasticizer selected from the group consisting of compounds represented by the following formula (1):
R1"Parenopenst"Oxe2x80x94R2"Parenclosest"mOOCxe2x80x94(CH2"Parenclosest"nCOO"Parenopenst"R3xe2x80x94O"Parenclosest"mR4xe2x80x83xe2x80x83(1) 
wherein R1 and R4 are the same or different alkyl groups having 1 to 30 carbon atoms or alkenyl groups, R2 and R3 are the same or different alkylene groups having 1 to 30 carbon atoms or alkenylene groups, m is an integer of 0 to 5, and n is an integer of 1 to 10,
and compounds represented by the following formula (2): 
wherein R5 is an alkyl group having 1 to 30 carbon atoms or alkenyl group.
Secondly, the above objects and advantages of the present invention are attained by a transfer film comprising a film forming material layer formed of the above inorganic particle-containing composition.
Thirdly, the above objects and advantages of the present invention are attained by a PDP production process which comprises the steps of transferring a film forming material layer constituting the above transfer film to the surface of a substrate and baking the transferred film forming material layer to form a dielectric layer on the substrate.
Fourthly, the above objects and advantages of the present invention are attained by a PDP production process which comprises the steps of transferring a film forming material layer formed of the above inorganic particle-containing composition to the surface of a substrate, forming a resist film on the transferred film forming material layer, exposing the resist film to form a resist pattern latent image, developing the resist film to form a resist pattern, etching the film forming material layer to form a pattern layer corresponding to the resist pattern, and baking the pattern layer to form a constituent element selected from the group consisting of a barrier, electrode, resistor, dielectric layer, phosphor, color filter and black matrix.
Fifthly, the above objects and advantages of the present invention are attained by a PDP production process which comprises the steps of forming a laminate film consisting of a resist film and a film forming material layer formed of the above inorganic particle-containing composition on a base film in the order named, transferring the laminate film formed on the base film to the surface of a substrate, exposing the resist film constituting the laminate film to form a resist pattern latent image, developing the resist film to form a resist pattern, etching the film forming material layer to form a pattern layer corresponding to the resist pattern, and baking the pattern layer to form a constituent element selected from the group consisting of a barrier, electrode, resistor, dielectric layer, phosphor, color filter and black matrix.